“It’s really exciting to discover that the detailed anatomy of the teeth has finally allowed us to identify precisely this important Canadian fossil,” said University of Toronto Mississauga (UTM) lead author Kirstin Brink.

“Dimetrodon is actually more closely related to mammals than it is to dinosaurs.”

In fact, it’s believed Dimetrodon went extinct some 40 million years before the dinosaurs.

The study – a collaboration with researchers from Carleton University and the Royal Ontario Museum – appeared in the November 23 issue of the Canadian Journal of Earth Sciences.

The fossil, previously known at Bathygnathus borealis, was collected in 1845 while a farmer was digging out a well on his property near French River, PEI.

As there were no natural history museums in Canada at the time the fossil was found, it was sold to the Academy of Natural Sciences in Philadelphia, where celebrated paleontologist Joseph Leidy could study and name it.

Leidy named the fossil Bathygnathus (meaning deep jaw) borealis (from the north) because he mistook it as the lower jaw of a dinosaur, similar to the large bipedal species that were being collected in Europe at the time.

“This greatly expands our knowledge of these early relatives of modern mammals, as well as the history of life in Canada,” said Carleton professor Hillary Maddin, noting  “it is an important part of understanding our natural heritage.”

The Bathygnathus specimen was the first ‘dinosaur’, and the second vertebrate fossil named from Canada — Dendrerpeton, anextinct amphibian from Nova Scotia, was named by Sir Richard Owen two months earlier.

Several paleontologists have studied the Bathygnathus specimen since it was first named, but its precise identity was unknown since it was unclear whether it had Dimetrodon’s signature dorsal sail, created by tissue stretched between spines sticking up from its backbone, or lacked a sail like its smaller cousin Sphenacodon.

Using family trees and imaging techniques to see the internal anatomy of the fossil, researchers found the eight preserved teeth linked the fossil to the Dimetrodon family — the first terrestrial animal to have ‘ziphodont’ teeth.

“These are blade-like teeth with tiny serrations along the front and back of the teeth, similar to a steak knife,” said senior author of the study, UTM professor Robert Reisz.

“The roots of these teeth are very long, around double the length of the crowns. This type of tooth is very effective for biting and ripping flesh from prey.”

Fossils of Dimetrodon have now been found in the USA, Canada and Germany.